[Cryptography] Uncorrelated sequence length, was: A TRNG review per day

Jerry Leichter leichter at lrw.com
Fri Oct 31 15:08:11 EDT 2014


On Oct 31, 2014, at 2:31 PM, Bear <bear at sonic.net> wrote:
>>> A provably long uncorrelated sequence length is the same kind of 
>>> "hard" guarantee as a one time pad -- although, like a one-time pad, 
>>> it applies only to sequences shorter than that length. 
> 
>> I don't know what this means.  Any *specific* property - like a long
>> uncorrelated sequence length - is just a special instance of a way of
>> distinguishing the output of some algorithm from a true random
>> sequence.
> 
> I am completely baffled by this comment. 
> 
> A provable uncorrelated sequence length of N or greater is a proof 
> that it is NOT even theoretically possible to distinguish any
> generated sequence having length less than N from a true random
> sequence.  That is the opposite of being a way to distinguish a
> generated sequence from a truly random sequence. 
The *test* "Has an uncorrelated sequence length of N or greater" is a special case of distinguisher from a random sequence.  Yes, if you are asking the question "Is this sequence distinguishable from a known random sequence?" you have to invert the output of the "USL > N" test, but that's a triviality.

BTW, I've responded based on the assumption that "uncorrelated sequence length" is actually a well-defined concept with a meaning based on the plain English words.  I just did what I should have done earlier:  A Google search in an attempt to find the technical definition.  The search finds exactly four instances of this exact phrase - all of them in the present discussion!  So I guess on the statement "Uncorrelated sequence length is a thing", the *correct* response is "citation needed".

                                                        -- Jerry

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4813 bytes
Desc: not available
URL: <http://www.metzdowd.com/pipermail/cryptography/attachments/20141031/07116331/attachment.bin>


More information about the cryptography mailing list